Slow freezing process design for human induced pluripotent stem cells by modeling intracontainer variation

Abstract

Abstarct This work presents a model-based design of slow freezing processes for human induced pluripotent stem (hiPS) cells considering quality variation inside a container. A single-cell model was developed that integrated heat transfer, mass transfer, and crystallisation models. These mechanistic models described the radial and temporal temperature profiles in a container, the volume change of a cell through transmembrane water transport, and intracellular ice formation during slow freezing, respectively. The integration enabled calculation of the maxima of the cell volume change and intracellular ice crystal volume, and the required freezing time, as a function of cooling rate, vial diameter, cryoprotective agent, and vial material. By this way, we could provide, for the first time, the intracontainer variation of cell quality, a critical factor towards industrial manufacturing of hiPS cells. Three design cases were explored where the optimal vial size was obtained given the cell demand for a specific freezer.